Transformer



J. V. FILL TRANSFORMER July 2, 1940.

Filed March 25, 1935 1 N VEN TOR. John 1/. F

36 37 ATTORNEYS.

Patented July 2, 1940 UNITED STATES FATENT OFFEQE TRAN SFORMER John V.Fill, New York,

N. Y., assignor to'Ferro- Application March 25, 1935, Serial No. 12,877

16 Claims.

This invention relates to coupling transformers adapted to pass only apredetermined, narrow band of frequencies, which find employmentprincipally in superheterodyne radio sets for passing intermediatefrequency voltage from one stage to another. The invention may be usedadvantageously, however, for effecting any radio frequency or other highfrequency coupling.

It is an object of the invention to provide a transformer structurewhich can be assembled economically and accurately, and in which thecircuits of the successive stages can be adjusted precisely to desiredresonance characteristics.

It is a further object of the invention to provide a novel methodwhereby devices of the class indicated may be accurately andeconomically manufactured.

Other objects and advantages will hereinafter appear.

In the drawing forming part of this specification Figure l is a sideelevation, with parts in section, of a structure embodying features ofthe invention, the stucture being shown as turned on its side;

Figure 2 is a side elevation of the same structure illustrated in Figure1, but with the shield can removed, and turned around so as to exposethe opposite side to view;

Figure 3 is a View in rear elevation of the structure of Figure 2;

Figure 4 is a sectional, detail view of the transformer supportingstructure, and

Figure 5 is a plan view of an insulating spacing plate employed in thedevice.

The transformer illustrated comprises a sleeve I of paper or othersuitable insulating material of accurately predeterminedtransversedimensions. The sleeve is desirably cylindrical, but may bemade polygonal if desired, and its walls are of substantially uniformthickness. Ferromagnetic core members 3 and 4 are inserted into and fitsnugly within the sleeve, the core member 3 being placed near one endthereof, and the core member 4 being placed at a predetermined distancefrom the core member 3. The core members are desirably composed ofpowdered iron, the iron particles being united by means of a suitableinsulating binder and molded.

A rod 5 of wood or other suitable insulating material is passed throughbores 6 and l of the core members 3 and 4. The rod fits the core memberssnugly so that the core members cannot shift longitudinally of the rod.The preferred method of making the assembly is to posi- (Cl. 250--l6)tion the core members properly upon the rod 5 and then insert the rodwith the core members mounted upon it into the sleeve I. The axis of therod coincides with the axis of the sleeve l.

After the assembly has been thus effected it is placed in a coil windingmachine which winds two coils 8 and 9 upon the sleeve simultaneously.The winding is effected by rotation of the sleeve about its axis, andthe wire supplying and guiding devices are so spaced, arranged, andmoved that identical coils are caused to be wound about the middleportions of the core members 3 and i. Desirably the same kind of wire isemployed for both coils and the winding of the coils is initiatedsimultaneously and terminated simultaneously. After the wiring has beencompleted the assembly is dipped in molten Wax which, upon solidifying,prevents penetration of moisture. The coils need not be identical in allinstances, since it is sometimes desirable to employ coupled coilsbearing different numbers of turns so as to step the voltage up or down.

A reduced, threaded stem portion Iii extends from an end of the rod 5,in axial alignment with the rod. An insulating condenser supportingblock 42 is impaled upon the stem H3, and a nut I3 is screwed onto thestem to clamp the block I2 in place. The nut I3 and the shoulder of therod 5 at the inner end of the stem l0 jointly fix the position of theblock I2 longitudinally of 130 the stem Ill.

The block I2 carries small, adjustable condensers M and I5 at oppositesides of the stem Ill. The condenser I4 comprises alternate conductiveand insulating plates i6 and H. Alternate conductive plates of thecondenser are connected to a terminal I8 and the other alternateconductive plates are connected to a terminal H9. The outermostconductive plate" of the condenser is resilient and is bowed. A screw 29is passed through the condenser plates without contacting them, andthrough the block I2, a nut 2| is threaded onto the screw 29. The nut His received in a recess in the block and is held by 45 the walls of therecess against rotation. Thescrew is separated from the outermostconductive plate of the condenser by an insulating washer 22 and ametallic washer 23. The screw and nut serve both to hold the condenserparts in place and to adjust the capacity of the condenser. The terminal13 is connected to the outer end of the coil 8 through a conductor 22a,and the terminal is is connected to the inner end of the coil 8 througha conductor 23a. The conductors 22a and 23a, are preferably wire endsintegral with the winding of the coil 8.

The condenser 15 is desirably identical in construction with thecondenser it, and will not be described in detail. It may, however, bemade to cover a different range of capacities if desired. Alternateconductive plates of the condenser l5 are connected to a terminal E i,and the other alternate conductive plates of the condenser are connected'to a terminal 25. The terminal 2 1 is connected to the inner end of thecoil 9 through a conductor 25, and the terminal 25 is connected to theouter end of the coil 9 through a conductor 27. The conductors 2% and 27are desirably integral end portions of the winding of the coil 9.

Conductors 28 and 29 are connected respectively to the terminals i8 andi9 and form elements of the stage of which the coil 8 and condenser I4form parts. Conductors'3i] and 31 are connected to the terminals 24 and25 and form elements of the stage of which the coil ii and the condenseri5 form parts.

Spacer plates 32 and 33 of insulating material are mounted upon thesleeve 5, the former substantially against the forward or upper face ofthe coil 9, and the latter substantially against the rear or lower faceof the coil 8. The spacer plates 32 and 33 are of insulating material,being desirably made of paper.

The spacer plate 32 is seen in Figure 5. It is provided with a centralopening 34 shaped to fit the sleeve I. A slit 35 extends from theopening 34 through the periphery of the plate so that the plate may bedeformed and passed around the sleeve I after the other described partshave been fully assembled. Adjacent each corner of the plate provisionis made of an open ing 36 for receiving one of the conductors 23, 29, 30and 3|, and each of these openings communicates through a slit 3'! withthe periphery of the plate so that the conductors can be inserted intothe openings 36 through the marginal portions of the plate.

The spacer plate 33 may be or identical construction but, as shown, thisspacer plate not provided with the slits 35 and 37!.

The spacer plates support the conductors 28, 29, 30 and 3| atpredetermined equal distances from the coils and from one another andcause them to extend in parallelism with the common axis of the coils.The inherent couplings between the conductors and the coils aretherefore substantially constant as the conductors cannot shift positionand thus cause changes in the resonant frequencies of the coils.

When the parts have been assembled as described, they are inserted intoa metallic, shielding housing 33 which substantially fits the insulatingblock i2 and the spacer plates 32 and 33. The stem iii is passed througha central opening in the top of the housing and is secured to thehousing by threading a nut 39 onto the stem. The housing is made longenough to extend a substantial distance beyond the end of the sleeve i,and hence serves to space the lower coil 8 a substantial distance awayfrom the supporting base or chassis section :10 upon which the housingis mounted. The coil 8 is thus protected against undesired inductiveinterference. The housing is provided with threaded legs M which arepassed through the supporting base and secured to the base by means ofnuts 42.

The housing is provided with openings 33 in its top face through whichaccess may be had to the adjusting screws 72E of the condensers M and l5after the parts have been fully assembled as described.

The structure shown and described is capable of being made veryaccurately and yet inexpensively. Because of the high degree of accuracywhich can be secured, receiving sets employing the disclosed structuremay be made to possess a very high degree of selectivity. In thisconnection it it of particular importance that the coupling between thecoils may be made of just the proper value to assure the maximumeiiiciency of transmission while avoiding the detuning of one circuit bythe other.

I have described what I believe to be the best embodiments of myinvention. I do not wish, however, to be confined to the embodimentsshown, but what I desire to cover by Letters Patent is set forth in theappended claims.

I claim:

1. In a high frequency coupling device for radio sets, in combination,an insulating support, an insulating rod and means securing one endthereof to said support, a pair of ferromagnetic cores each comprisingpowdered magnetic material having the form of a cylinder with a boreextending axially therethrough, said cores being mounted upon the rod atpredetermined positions longitudinally thereof, a single insulatingsleeve conforming to and snugly fitting the cores, transformer coilsmounted upon the sleeve around the mid-portions of the respective cores,and means for mounting said support on a chassis.

2. In a high frequency coupling device for radio sets, in combination,an insulating sleeve having a wall of substantially constant thickness,a pair of ferromagnetic cores each comprising powdered magnetic materialhaving the form of a cylinder with a bore extending axiallytherethrough, said cores being mounted in the sleeve in predeterminedpositions longitudinally thereof, transformer coils fixed upon thesleeve around the mid-portions of the respective cores, and meansincluding a rod extending through said sleeve and secured to said coresfor mounting the assembly.

3. In a high frequency coupling device for radio sets, in combination,an insulating sleeve having a wall of substantially constant thickness,a pair of ferromagnetic cores each comprising powdered magnetic materialhaving the form of a cylinder with a bore extending axiallytherethrough, said cores being mounted in the sleeve in predeterminedpositions longitudinally thereof, identical transformer coils wound insitu upon the sleeve around the respective cores, and means including arod of non-magnetic material snugly fitted within said cores formounting said coupling device on a support.

4. A high frequency transformer for radio sets comprising a block ofinsulating material, a paper insulating tube and means mounting the sameupon said block, a pair of ferromagnetic cores mounted in predeterminedspaced relation within said tube, a transformer coil at the exterior ofand fixed to said tube around the mid-portion of each core, conductivemembers extending from the terminals of said coils, and spacer plates ofinsulating material mounted on said tube adjacent said coils andextending outwardly beyond said coils, said spacer plates havingopenings for receiving and retaining said conductive members in fixedposition with respect to said coils.

5. In a transformer for radio sets, an insulating block, a pair ofadjustable condensers moun1;

ed on one face of the block, a rod of insulating material secured to andextending from the opposite face of said block, a pair of tubular coresof magnetic material fitted upon said rod in axially spaced relation, apair of coaxial transformer coils mounted about and insulated from therespective cores in predetermined spaced relation, said condensers beingshunted across the respective coils, a shield housing having a topthrough which said rod extends, means threaded on the extended end ofthe rod to secure the same to the top of said housing, thereby tosuspend said rod and cores and coils thereon from the top of saidhousing, means at the other end of said housing for mounting the same ona chassis, the top of the housing being apertured for access to saidcondensers to adjust the same.

6. In a transformer for radio sets, an insulating block, a pair ofadjustable trimming condensers on one face of said block, an insulatingsleeve extending from the opposite face of said block, a pair of axiallyspaced cores within said sleeve, transformer coils on said sleeve andsurrounding the respective cores, said condensers being shunted acrossthe respective coils, a shield housing telescoped over said block andsleeve from the block end thereof, means including a threaded rodattached to said sleeve securing said sleeve to said block, meansincluding said threaded rod suspending said block from the top of saidhousing, apertures in the top of said housing affording access to saidcondensers for adjusting the same, and means at the bottom of saidhousing for mounting the same on a chassis.

'7. The method of making a radio frequency transformer of the typeincluding an insulating sleeve, tubular ferromagnetic cores on an insulating rod and within the sleeve, and transformer coils surrounding therespective cores, said method comprising mounting the cores on the rodin predetermined spaced relation, inserting the assembled rod and coresinto the sleeve in predetermined position longitudinally thereof, andthen winding a pair of transformer coils simultaneously on said sleeveand about the respective cores.

8. The method of making a radio frequency transformer of the typeincluding an insulating sleeve, tubular ferromagnetic cores on aninsulating rod and within the sleeve, and transformer coils surroundingthe respective cores, said method comprising mounting the cores on therod in predetermined spaced relation, inserting the assembled rod andcores into the sleeve in predetermined position longitudinally thereof,and then winding a pair of identical transformer coils simultaneously onsaid sleeve and about the mid-portion of the respective cores.

9. In a radio frequency transformer, in combination with an insulatingrod, a pair of ferromagnetic cores of tubular form mounted on and snuglyfitting said rod, windings surrounding each of said cores, a singleelongated sleeve of insulating material surrounding said rod and snuglyfitting said cores and means for securing one end of said rod to achassis, thereby to mount said transformer on the chassis.

10. A transformer as claimed in claim 9, wherein said mounting meanscomprises a shield can enclosing said transformer having an upperapertured end through which one end of said rod extends, means on theextended end of said rod to secure the same to said can to suspend saidtransformer therefrom, and means at the opposite end of said can forsecuring the same to a chassis.

11. A transformer as claimed in claim 9, wherein said mounting meanscomprises a block of insulating material having an opening through whichone end of said rod extends, means securing said block to said rod infixed position thereon, and a shield can enclosing said block andtransformers, the end of said rod which projects through said blockbeing secured to said can to mount said transformer and block within thesame.

12. In a tuned coupling circuit for radio receivers, the combination oftwo members of insulating material spaced from each other and insubstantially parallel relation, an element of nonconducting materialsupported between said members, inductively related high-frequencyinductance coils supported by said element between said members, coresof magnetic material for said coils, conductor members extending betweensaid insulating members near said coils, said conductor members beingspaced from each other and from said coils in predetermined positions bysaid insulating members and being electrically connected respectivelywith the terminals of said coils, and tuning condensers carried by oneof said members and having terminals electrically connected respectivelywith said conductor members, whereby the coils are tuned by saidcondensers to form coupled resonant circuits and said conductor membershave fixed capacitive couplings with the coils with which they are notconnected.

13. In a tuned coupled unit for radio receivers, the combination of twoheads of insulating material spaced from each other and in substantiallyparallel relation, a supporting element of non-conducting materialconnecting and secured to the central portion of said heads, annularcores of magnetic material secured to said supporting element,high-frequency coils around said cores, the relation of said coresinductively coupling said coils, conductor members spaced from eachother and from said coil and extending between said heads, saidconductor members being substantially parallel with each other and withsaid supporting element and electrically connected respectively withterminals of said coils, and tuning condensers carried by one of saidheads and having electrical terminals connected respectively with saidconductor members connected to the coils to be tuned by said condensersto form coupled resonant circuits, whereby said conductor members havefixed capacitive coupling with the coils with which they are notconnected, said condensers having connection lugs connected directlywith said conductor members.

14. In a tuned coupled unit for radio receivers, the combination of twoheads of insulating ma terial spaced from each other and insubstantially parallel relation, a supporting element of non-conductingmaterial connecting and secured to the central portion of said heads,annular cores of magnetic material secured to said supporting element,high-frequency coils around said cores, the relation of said coresinductively coupling said coils, conductor members spaced from eachother and from said coil and extending between said heads, saidconductor members being substantially parallel with each other and withsaid supporting element and electrically connected respectively withterminals of said coils, and tuning condensers carried by one of saidheads and having electrical terminals connected respectively with saidconductor members connected to the coils to be tuned by said condensersto form coupled resonant circuits, whereby said conductor members havefixed capacitive coupling with the coils with which they are notconnected, said conductor members extending through the head remote fromsaid condensers and comprising connection terminals for said tunedcoupling unit.

15. In a high-frequency resonant coupling unit for radio receivers, thecombination of an insulating support, inductance coils mounted ininductive relation to each other on said support, adjustable condensershaving fixed relation to said support for tuning said coils, saidcondensers having connection terminals, conductor members connectedelectrically to the terminals of said coils and to the connectionterminals of said condensers, and means retaining said conductor membersin fixed relation to said support near said coils, thereby establishingfixed capacitive effects between said conductor members and other partsof said coupling units.

7 16. In a high-frequency resonant coupling unit for radio receivers,the combination of a supporting rod of non-magnetic material, annularmagnetic cores mounted in fixed position on said rod, inductive windingsaround said cores, a base of insulating material secured to one end ofsaid rod, adjustable condensers mounted on said base for tuning saidwindings, conductor members spaced from said windings, and means holdingsaid conductor members sub stantially parallel with said supporting rodand with each other, said conductor members being electrically connectedto the terminals of said condensers and the terminals of said windings,whereby fixed capacitive effects are established between said conductormembers and the other parts of the coupling unit.

JOHN V. FILL.

